Large-scale Energy Storage Technologies Research Articles

Synergetic bifunctional Cu-In alloy interface enables Ah-level Zn metal pouch cells

Rechargeable aqueous zinc-metal batteries, considered as the possible post-lithium-ion battery technology for large-scale energy storage, face severe challenges such as dendrite growth and hydrogen evolution side reaction (HER) on Zn negative electrode. Herein, a three-dimensional Cu-In alloy interface is developed through a facile potential co-replacement route to realize uniform Zn nucleation and HER anticatalytic effect simultaneously. Both theoretical calculations and experimental results demonstrate that this bifunctional Cu-In alloy interface inherits the merits of low Zn-nucleation overpotential and high HER overpotential from individual copper and indium constituents, respectively. Moreover, the dynamical self-reconstruction during cycling leads to an HER-anticatalytic and zincophilic gradient hierarchical structure, enabling highly reversible Zn chemistry with dendrite-free Zn (002) deposition and inhibited HER. Moreover, the improved interface stability featured by negligible pH fluctuations in the diffusion layer and suppressed by-product formation is evidenced by in-situ scanning probe technology, Raman spectroscopy, and electrochemical gas chromatography. Consequently, the lifespan of the CuIn@Zn symmetric cell is extended to more than one year with a voltage hysteresis of 6 mV. Importantly, the CuIn@Zn negative electrode is also successfully coupled with high-loading iodine positive electrode to fabricate Ah-level (1.1 Ah) laminated pouch cell, which exhibits a capacity retention of 67.9% after 1700 cycles.

Thermodynamic analysis and optimization of the TI-PTES based on ORC/OFC with zeotropic mixture working fluids

Thermal Integrated Pumped Thermal Energy Storage (TI-PTES) is a promising technology for large-scale energy storage attributed to the advantages of geographical independence, high efficiency, low cost, and easy coupling with other systems. Little research has been dedicated to TI-PTES based on the organic flash cycle (OFC). This study established thermodynamic analysis of the TI-PTES based on the organic Rankine cycle (ORC) and OFC. The effects of system configurations and key parameters are explored. A multi-objective optimization is introduced to optimize the ORC-TI-PTES, and the P2P efficiency of 57.18 %, exergy efficiency of 37.47 %, and ESD of 4.4 kWh/m3 are achieved. The potential application of zeotropic mixture working fluids in the OFC-TI-PTES is investigated. The DOFC-TI-PTES with [R365mfc(60 wt%) + R1234ze(Z)] shows the best performance among the four OFC configurations. The achieved P2P efficiency and exergy efficiency are 46.66 % and 29.18 %, lower than the ORC-TI-PTES. However, the DOFC-TI-PTES provides an ESD of 11.487 kWh/m3, which is significantly higher than that of the ORC-TI-PTES. ORC-TI-PTES is suitable for energy storage applications that prioritize high thermal and exergy efficiencies, whereas OFC-TI-PTES is suitable for scenarios requiring high ESD.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials.

Sodium-ion batteries (SIBs) as a promising technology for large-scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode-electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra-stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM-CS-GMg) cathode material in which a Mg-free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg-hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered-to-rock-salt phase transition and the resultant microcracks. Besides, the less formation of high-valence TM ions on the surface contributes to a stable cathode-electrolyte interface. The as-prepared NCM-CS-GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Pd2+-coordinated polybenzimidazole membranes with fast and selective ion transport for alkaline aqueous organic redox flow battery

The advancement of aqueous organic redox-flow batteries (AORFBs) is impeded by the lack of efficient, low-resistance, and highly selective ion-conducting membranes (ICMs). Although polybenzimidazole (PBI) is one of the most promising low-cost non-fluorinated ion-conducting membranes, it remains challenging to design stable PBI membranes with fast and selective ion transport channels. Here, we engineer the chemical structure of PBI and regulate the ion transport channels to prepare highly conductive and selective Pd2+-coordinated membranes with grafting and crosslinking structures. In this design, the positively charged quaternary ammonium groups on the side chain improve the conductivity of OH−, while the continuous cross-linked network formed by ionic bonds between quaternary ammonium groups and deprotonated imidazole groups significantly enhances the membrane's mechanical properties. Furthermore, the coordination of Pd2+ with PBI and plasticization of PBI chain by trifluoroacetate anions expand the molecular free volume while inducing local contraction. Consequently, the QPBI-xPBI-Pd membrane enables fast charge carrier transport and suppresses the diffusion of active substances. The AORFBs assembled with the QPBI-10PBI-Pd membranes exhibit high coulombic efficiency (99.6 %) and energy efficiency (77.67 %) at 100 mA cm−2, maintaining excellent stability for 500 cycles. This study provides an innovative strategy to design high-performance PBI membranes for RFBs, thereby advancing the viability of RFBs in the realm of large-scale energy storage technologies.

Revitalizing Dead Zinc with Ferrocene/Ferrocenium Redox Chemistry for Deep-Cycle Zinc Metal Batteries.

Aqueous zinc (Zn) batteries are highly desirable for sustainable and large-scale electrochemical energy storage technologies. However, the ceaseless dendrite growth and the derived dead Zn are principally responsible for the capacity decay and insufficient lifespan. Here, we propose a dissolved oxygen-initiated revitalization strategy to reactivate dead Zn via ferrocene redox chemistry, which can be realized by incorporating a trace amount of poly(ethylene glycol) as a solubilizer to improve the solubility of water-insoluble ferrocene derivatives. Ferrocene scaffold can be spontaneously oxidized to ferricenium cations by dissolved oxygen, which eradicates the dissolved oxygen-involved Zn corrosion and insulating by-product generation. Subsequently, the generated ferricenium cations as the scavenger can rejuvenate electrically isolated dead Zn into electroactive Zn2+ ions to compensate the zinc loss. Through this design, the symmetric cell exhibited improved cycle life of 3700 h at 10 mA cm-2, and 220 h under a high depth of dischargeof 80%. Importantly, the Zn||NaV3O8·1.5H2O full cells demonstrated the impressive cycling stability over 1000 cycles at a low N/P ratio of 3.0. This work presents an innovative solution for the revitalization of dead Zn to extend the lifespan of deep-cycling metal batteries.

Airtightness evaluation of lined caverns for compressed air energy storage under thermo-hydro-mechanical (THM) coupling

Large-scale compressed air energy storage (CAES) technology can effectively facilitate the integration of renewable energy sources into the power grid. The airtightness of caverns is crucial for the economic viability and efficiency of CAES systems. This paper presents a new thermo-hydro-mechanical (THM) model for investigating the effects of complex thermodynamic changes on air leakage in concrete-lined rock caverns. The model is validated using field measurement data, numerical simulations, and analytical solutions. Subsequent simulations were conducted to analyze air leakage, pore pressure, and leakage range under various operating conditions. Finally, the impacts of different parameters on air tightness were assessed. The results indicate that the daily air leakage mass percentage (TDALMP) in the concrete-lined CAES cavern is 0.60 % under the operating pressure of 4.5–10 MPa, which meets the tightness requirement. The permeability of the lining is a key parameter for airtightness, in this case, the permeability of the concrete lining cannot exceed 1 × 10−19 m2. The daily air leakage rate can be reduced by modestly increasing the cavern radius, lowering the temperature of the injected air, and decreasing the maximum operating pressure. These results can provide a reference for the study and construction of CAES caverns in similar projects.

Stable Cycling of Ultrahigh Mass Loaded MnO2 for Low-Cost Sodium-Ion Batteries

Achieving cost-effective and sustainable solutions for large-scale energy storage is critical for advancing the global clean energy transition. The intermittent nature of green energy underscores the inadequacy of current large scale energy storage technologies like pumped hydroelectricity which is susceptible to geographic and water resource constraints, making batteries a prime candidate for this role. Although lithium-ion batteries (LIBs) with high energy and power density are a viable solution, the high cost and uneven distribution of lithium reserves limits the widespread application of LIBs for grid energy storage. Considering these developments and the challenges posed by limited lithium reserves, sustainable and low-cost sodium-ion batteries (SIBs) emerge as a promising alternative.Among the various battery electrode materials, manganese dioxide (MnO2) stands out as a promising choice for large-scale energy storage applications due to its earth abundance, cost-effectiveness and non-toxic nature. Although MnO2 is known as a pseudocapacitive material with superior cycling stability in aqueous electrolytes, its dissolution in non-aqueous electrolytes has restricted its widespread use in long lifetime batteries. In this study, we demonstrate that an ether-based electrolyte solution (1M NaClO4 in diglyme) is able to achieve stable cycling of electrodeposited ε-MnO2 as a cathode for SIBs, reaching a over 75% capacity retention over 1000 cycles. This response surpasses conventional ester-based electrolytes (58% of 1M NaClO4 in EC/PC). A comparative cycling stability study, coupled with electrochemical quartz crystal microbalance characterization, validates the efficacy of the ether-based electrolyte in mitigating MnO2 dissolution. Furthermore, the integration of 3D printed graphene aerogel (3D GA) as a scaffold for electrodeposited MnO2 leads to enhanced electrochemical performance of the MnO2 electrode (3D MnO2/GA), resulting in a high areal capacity of 4.4 mAh cm-2 at a current density of 10 mA cm-2. The 3D MnO2/GA electrode possesses scalable electrochemical performance with mass loadings from 20 mg cm-2 to 80 mg cm-2. Using this electrode, a high mass loaded sodium-ion battery (SIB) device was fabricated by using utilizing 58 mg cm-2 3D MnO2/GA as the cathode and 16 mg cm-2 dip-coated TiO2@Cu foam as the anode. This MnO2 | TiO2 device delivered a notable areal capacity of 6.2 mWh cm-2 and a high areal power density of 70.7 mW cm-2. Moreover, the SIB device demonstrates 85% capacity retention after 500 cycles, underscoring the stable cycling of this high-energy and power-density SIB device.

Lunar Electrochemistry Enabling Microgrid Energy Storage on the Moon

This talk will cover an atypical paradigm of large scale energy storage technology - the need for scalable energy storage using resources available at the point of use for sustained human presence in space exploration. For Lunar surface power reliability, large scale energy storage enables increased safety factor for power generation downtime, but the launch mass of energy storage makes scalable storage to the level of microgrids or grids unappealing. This is compounded by a central paradox of safe energy storage, that achieving high energy density intrinsically carries greater safety risk in storing greater energy in a smaller mass or volume. In situ resource utilization aims to solve both these problems, enabling safe and scalable energy storage to be deployed for Lunar surface power reliability. However, a long road remains between the nascent field of ISRU energy storage as it exists today and its needed destination to enable future sustained human presence on the Moon and Mars.This talk will survey applications of electrochemical energy storage technologies and concepts with a focus on how Lunar resources can principally drive the electrochemistry. Brief mention will be given to non-electrochemical technologies such as thermal or mechanical methods, but the emphasis will be on electrochemistry owing to rapid advances in electrochemical state-of-the-art on Earth. Examples will include beyond Li-ion intercalation chemistry, metal-air cells, redox flow batteries, and regenerative fuel cells, using Lunar regolith and water as primary resources. For each technology, the talk will highlight where the study of “Lunar electrochemistry” must deviate from current terrestrial research to enable energy storage optimized for ISRU, rather than a simple transplant of Earth technology to Lunar application.

Disulfide bonded polyimide cathode of rechargeable magnesium batteries: Improved capacity via reversible break/formation of disulfide and sulfur-oxygen bonds

Rechargeable magnesium batteries are a potential selection for large-scale energy storage technologies, but development of cathode materials is the major difficulty at present. Organic polyimides are promising magnesium battery cathodes with the open and amorphous frameworks as well as enhanced charge delocalization. However, only two carbonyls are redox-active out of four for each imide unit, which largely limits the capacity. Herein, a new polyimide containing disulfide bond is fabricated and studied as cathode for rechargeable magnesium batteries. This polyimide shows a high capacity beyond the traditional two-electron principle. A mechanism study demonstrates that carbonyl enolization and disulfide bond break/formation occur in the redox process, leading to formation/break of sulfur-oxygen bond. This sulfur-oxygen bond enhances enolization and electron delocalization, resulting in an improved capacity. Further theoretical computation indicates a charge transfer within this sulfur-oxygen bond. The two-electron reduction state exhibits quite low HOMO and LUMO energy levels, which makes the disulfide bonded polyimide have a higher tendency to accept more electrons and a higher oxidation stability after reduction.

Redox mediator enabling fast reaction kinetics and high utilization of iodine in aqueous iodine redox flow battery

Aqueous iodine redox flow batteries (AIRFBs) have been identified as a promising technology for large-scale energy storage. However, practical capacity of AIRFBs is limited by the relatively low utilization of iodine caused by the low reaction kinetics. Here, we report an electrode modified by cobalt hexacyanoferrate (CoHCF), which supports a redox-mediating process developing alternative redox reaction pathways of iodine with reduced redox activation energies. Contributed by the strong adsorption of iodine by CoHCF, redox reaction kinetics of iodine species is accelerated, and the utilization of iodine in batteries is increased. Applying the CoHCF modified carbon felt as cathode electrode, the constructed zinc-iodine redox flow battery exhibits a high iodine utilization reaching 95.59% of the theoretical capacity at a current density of 20 mA cm−2, which enhances 139.89% comparing to the battery without electrode modification. The redox mediator-based electrode enabling fast reaction kinetics and high utilization of iodine species offers a promising strategy enhancing the battery performance thereby advancing the development of AIRFBs.

Performance study of a compressed air energy storage system incorporating abandoned oil wells as air storage tank

With the rapid development of intermittent renewable energy, large-scale compressed air energy storage technology represented by Adiabatic Compressed Air Energy Storage (A-CAES) has attracted much attention. In order to simultaneously solve the problems of reuse of decommissioned oil wells and low efficiency of A-CAES system, a compressed air energy storage system incorporating abandoned oil wells as Air Storage Tank (AST) is proposed in this paper. The system performance of underground Oil Well CAES (OW-CAES), aboveground Steel Pipeline CAES (SP-CAES), and aboveground Storage Tank CAES (ST-CAES) is comparatively analyzed based on a thermodynamic model, focusing on the impact of heat transfer characteristic parameters of the AST wall on the system performance. The results show that recoverable heat and round-trip efficiency are significantly affected by the heat transfer characteristics of the AST wall. More recoverable heat and higher round-trip efficiency can be achieved by increasing the wall temperature and the surface area of the AST, respectively. The round-trip efficiency and energy storage density of the OW-CAES system are higher than those of the ST-CAES system, which are increased by 8.3 % and 18.45 % respectively. This study provides theoretical support for the feasibility of the OW-CAES system and has certain engineering guiding significance.

The impacts of geothermal gradients on compressed carbon dioxide energy storage in aquifers

Compressed CO2 energy storage in aquifers (CCESA) is new low-cost large scale energy storage technology. To further improve the energy efficiency of CCESA, we propose to combine the geothermal system with CCESA. In order to study the influence of geothermal energy on CCESA, aquifers with large vertical interval and different geothermal gradients from 0.026–0.07 °C/m are designed. The 3d wellbore-reservoir grid of underground part of CCESA was established. The simulation covering 100 days of intermittent initial gas fill and 50 days of cyclic injection and production was conducted. The hydrodynamic and thermodynamic behaviors and energy efficiency of the system were analyzed, comparatively. In the gas fill period, the higher the geothermal gradient, the farther the front of CO2 plume diffuses in the target aquifer, and thus the smaller the pressure accumulation. The temperature, pressure and energy efficiency of produced CO2 increases with the increase of geothermal gradient, while the density of released fluid decreases. The energy efficiency is greater than 1.0 under 6 geothermal gradients. The average energy efficiency of high- and low-pressure reservoirs can reach 1.282 and 1.061 under the geothermal gradient of 0.07 °C/m, which is 21.79 % and 5.5 % higher than that of 0.026 °C/m. The total energy efficiency of the joint system finally can reach 95.1 %. This research well confirms that the geothermal energy can dramatically improve the efficiency of CCESA and can enhance its application.

Optimal capacity and multi-stable flexible operation strategy of green ammonia systems: Adapting to fluctuations in renewable energy

The potential of power-to-ammonia is increasingly recognized as a large-scale renewable electrical energy storage technology in the energy-transition landscape. Unlike conventional, continuously operating Haber-Bosch production processes, power-to-ammonia processes face operational challenges stemming from fluctuations in renewable power supply. Systematic strategies that can adapt to these fluctuations are required to improve the operational flexibility and stability of power-to-ammonia processes for industrial applications. This study proposes a multi-stable flexible ammonia operation strategy, which is practical and feasible in engineering. To maximize net profit, a design scheduling coordination optimization model is established and solved using a two-stage algorithmic framework of particle swarm and mixed integer linear programming. Additionally, three flexible scenarios are designed for the simulation analysis of a grid-connected green ammonia system. Compared with the traditional constant inflexible scenario, the multi-stable flexible scenario increases annual net profit by 5.05 M$ and reduces carbon emission intensity by 1.61 kg CO2/kgNH3. Furthermore, compared with the continuous flexible scenario, the volatility of the ammonia production load is reduced by 79.89 %. The multi-stable flexible operation strategy balances the green ammonia system’s economic, safety, and low-carbon attributes. Sensitivity analysis reveals that wind and photovoltaic complementary power generation reduces green ammonia costs and carbon emissions. When the selling price of ammonia exceeds 550 $/t, ammonia production and sales should be prioritized, but at lower ammonia prices, selling electricity to the grid to optimize economic efficiency is advised. This study provides novel insights into the flexible operation of the power-to-ammonia process and is expected to offer guidance for constructing and operating green ammonia systems.

Performance analysis and optimisation of waste heat recovery system based on zeotropic working fluid

As a new type of energy storage technology utilizing thermal energy, the Carnot battery is one of the most promising large-scale energy storage technologies due to its unlimited geographical conditions, simple structure, and high energy storage density. In this work, a thermodynamic model is established for a Carnot battery energy storage system that makes full use of waste heat resources, and the effects of the heat storage temperature, the components and mass fractions of the zeotropic working fluids on the various performances of the system are investigated. The temperature matching of the working fluids with different temperature glides in the heat exchangers are analyzed by using different mass fractions of R1234ze(E)/ R601a in heat pump and organic Rankin cycle systems, and the exergy flow charts and exergy loss of each component in the system are further investigated. The results show that the selection of the zeotropic working fluid with an appropriate temperature glide can effectively improve the system performance by improving the temperature matching degree and reducing the exergy loss in the heat transfer process. Compared with the evaporator, the temperature match of the condenser plays a more important role in the system performance. The use of R1234ze(E)/R601a in the heat pump improves the cofficient of performance by 4.46%-8.98% compared with that of pure R601a when the heat storage temperature increases from 110.0℃ to 140.0℃, and the use of zeotropic working fluid in the organic Rankin cycle also improves the performance by 8.12%-11.58%. For the power recovery of the whole pumped thermal energy storage system, the power-to-power efficiency improvement of the system using R1234ze(E)/R601a is 12.69%-20.11% and that using R1234yf/R601a is 12.46%-17.73% compared with the use of pure R601a. The power-to-power efficiency of R1234ze(E)/R601a (60/40) and R1234ze(E)/R601a (20/80) in the heat pump and organic Rankin cycle, respectively, are as high as 73.93% at a heat storage temperature of 130.0℃, which is 19.75% higher than the 61.74% for pure R601a.

Investigation of an integrated liquid air energy storage system with closed Brayton cycle and solar power: A multi-objective optimization and comprehensive analysis

Energy storage has garnered global attention as a promising solution to the intermittent nature of renewable energy sources. For large-scale (>100 MW) energy storage technology, there are only three types: Pumped Hydroelectric energy storage (PHES), Compressed air energy storage (CAES) and Liquid air energy storage (LAES). The limitation of PHES is that several natural geological features are needed. The traditional CAES needs a combustion chamber, which will result in environmental problems. LAES offers several advantages over traditional CAES systems, including higher energy density, scalability, flexibility in site selection, lower environmental impact, cost-effectiveness, and compatibility with renewable energy sources. Under these conditions, LAES is more suitable than other systems. This investigation examined a novel zero-carbon system integrating LAES with CBC and solar power. The primary objective is to maximize the round-trip efficiency (RTE) of the system while simultaneously minimizing the total investment cost per unit of output power (ICPP). By systematically exploring the trade-offs between RTE and ICPP, the study seeks to identify the proposed system’s most efficient and economically viable configurations. Each subsystem was simulated using Aspen Plus® V12 and validated against actual plant data. The analysis indicates that the proposed optimal LAES-CBC system could achieve a remarkable increase in RTE up to 67.81 %, representing an increase of 11.18 % compared to the baseline. Additionally, the total ICPP could be reduced to 0.2739 $/kWh, marking a decrease of 5.96 %. The charging process of the LAES system emerges as a critical focal point due to its significant contributions to exergy destruction and equipment costs. This study provides valuable insights into enhancing and achieving maximum efficiency and cost-effectiveness. These insights are essential for accelerating the transition towards a carbon–neutral energy system, highlighting the importance of research in advancing sustainable energy technologies.

Revealing electricity conversion mechanism of a cascade energy storage system

With the increasing penetration of renewable energy in the power system, it is necessary to develop large-scale and long-duration energy storage technologies. Deploying pump stations between adjacent cascade hydropower plants to form a cascade energy storage system (CESS) is a promising way to accommodate large-scale renewable energy sources, yet the mechanism how renewable curtailment is converted to hydroelectricity is still unclear. In this paper, we aim to clarify this mechanism by evaluating the CESS's long-term operational efficiency and changes compared to the cascade hydropower system. First, operational features and principle of the CESS was outlined. Then, long-term operations of the CESS and cascade hydropower system were, respectively, optimized using a simulation-based optimization framework. Finally, the operational efficiency of the CESS, defined as a ratio of reduced renewable energy curtailment to increased hydropower production, was calculated based on the above two optimized operation results. China's Longyangxia-Laxiwa CESS was selected as a case study. Results show that: (1) long-term operational efficiency of the CESS reached 81.6 %, i.e., 81.6 % of the curtailed renewable could be converted to hydroelectricity; (2) the increase in hydropower production was mainly attributed to the upper hydropower plant, accounting for about 96.5 % of the total increment; and (3) the increase in generation flow was the main factor to impact the increased hydropower production of the upper plant, although it could decrease the hydropower plant's hydraulic head.

Anodic Electrolysis Strategy Enabled Fe/FeCl2 Electrode for Scalable Fe/FeCl2-Graphite Molten Salt Battery.

The Fe/FeCl2-Graphite molten salt battery is a promising technology for large-scale energy storage, offering a long lifespan, a low operating temperature (<200 °C), and cost efficiency. However, its practical applications are hindered by the lack of a scalable preparation approach and insufficient redox stability in the Fe/FeCl2 electrode. Our study introduces an electrochemical anodic electrolysis (EAE) strategy, employing the anodic process (Fe → Fe2+) in an Al|AlCl3/NaCl/LiCl|Fe electrolysis system for the Fe/Fe2+ negative electrode in the Fe/FeCl2-Graphite battery. The EAE strategy forms an oxidized film, preventing incipient dissolution in the electrolyte and addressing redox stability issues with FeCl2 as the active substance. The Fe/Fe2+ negative electrode prepared by the EAE strategy exhibits a stabilized capacity of 0.72 mAh/cm2 after 7000 cycles at 5 mA/cm2, with a lower polarization level (∼29 mV) compared to FeCl2 as the active component. The flexibility of the EAE strategy is validated in both galvanostatic and potentiostatic processes, with a discharge capacity of 14 mAh after 1000 cycles, a capacity retention rate of 85%, and a Coulombic efficiency of 98% in the potentiostatic anodic electrolysis Fe/Fe2+ electrode. The scalability and reliability of the EAE strategy are further demonstrated in capacity-expanded Fe/FeCl2-Graphite batteries, reaching a discharge capacity of 155.1 mAh after 1000 cycles at 130 mA, with a capacity retention rate of 94%. For the first time, we showcased an EAE approach capable of producing Fe/Fe2+ electrodes at a rate of about 68.6 m2 per day. Additionally, we successfully assembled an Fe/FeCl2-Graphite battery at about a 0.42 ampere-hour level, paving the way for the scalable application of Fe/FeCl2-Graphite batteries.

The underground performance analysis of compressed air energy storage in aquifers through field testing

Compressed air energy storage in aquifers (CAESA) has been considered a potential large-scale energy storage technology. However, due to the lack of actual field tests, research on the underground processes is still in the stage of theoretical analysis and requires further understanding. In this study, the first kilometer depth compressed air injection-production field test with multiple flat aquifers is controlled. For all three production rates considered, the minimum pressure drop rate can reach 0.9 MPa/h. An actual wellbore-aquifer-coupled numerical model simulated by T2Well/EOS3 is verified using monitoring data. Due to the limitation imposed by the injection rate, air only flows into the top three sandstone aquifers to build air bubbles. During the production stage, air is first produced from the aquifers and then the air stored in the wellbore is gradually extracted due to the weakened air bubble support effect. Finally, an air-water two-phase occurs and the water level rises in the wellbore. Considering a hypothetical long-term cycle, the designed single aquifer scheme has a better underground performance. A concentrated and larger high air saturation domain can support a stable cycle pressure and above 95% underground efficiency. However, the wellhead pressure drops once water coning happens in the wellbore. With an air bubble replenishment scheme in each cycle, it becomes feasible to maintain stable pressure, ensuring a production pressure difference below 0.94 MPa without water production, over a 100-day cycle in the field. The results provide support for future practical engineering applications.

Projected effective energy stored of Zhangshu salt cavern per day in CAES in 2060

As a large-scale energy storage technology, compressed air energy storage (CAES) has the advantages of high efficiency and high reliability. This paper analyzed the feasibility of CAES cavern constructed in salt mine with multi-interlayer in Zhangshu, Jiangxi Province. Salt mine in Zhangshu is a typical bedded rock salt, and a method for calculating the cavern volume in Zhangshu was proposed. Using the proposed volume calculation method, it is expected that the volume of Zhangshu salt caverns can reach 27,840,000 m3 by 2060. By modelling the geomechanics used to calculate its stability. Based on the results of the simulation, the recommended operating pressure is 8.5–11.5 MPa. Finally, If this volume is used for CAES, the cycle pressure is assumed to be 8.5–11.5 MPa, energy storage efficiency of 50 %, the daily effective energy storage is 8.062 × 1014 J. This study will guide the development of the Zhangshu Salt Mine, provide lessons for similar areas and have a positive impact on the energy transition in Jiangxi.

A Review of Capacity Decay Studies of All-vanadium Redox Flow Batteries: Mechanism and State Estimation.

As a promising large-scale energy storage technology, all-vanadium redox flow battery has garnered considerable attention. However, the issue of capacity decay significantly hinders its further development, and thus the problem remains to be systematically sorted out and further explored. This review provides comprehensive insights into the multiple factors contributing to capacity decay, encompassing vanadium cross-over, self-discharge reactions, water molecules migration, gas evolution reactions, and vanadium precipitation. Subsequently, it analyzes the impact of various battery parameters on capacity. Based on this foundation, the article expounds upon the significance of battery internal state estimation technology. Additionally, the review also summarizes domestic and international mathematical models utilized for simulating capacity decay, serving as a valuable reference for future research endeavors. Finally, through the comparison of traditional experimental methods and mathematical modeling methods, this article offers effective guidance for the future development direction of battery state monitoring. This review generally overview the problems related to the capacity attenuation of all-vanadium flow batteries, which is of great significance for understanding the mechanism behind capacity decay and state monitoring technology of all-vanadium redox flow battery.